The present invention relates to a mechanism for assuring the separation of adjacent documents, such as sheets, in a stack thereof.
The invention will find particular application in connection with the handling of paper money. However, it is useful in other areas as well. In machines of this type it is necessary initially to separate the documents in the stack from one another so they can be individually counted or otherwise processed. Machines of this type are shown in applicant's prior U.S. Pat. Nos. 4,216,952 and 4,253,615 and in application Ser. No. 205,783 filed Nov. 10, 1980.
The above-mentioned prior art discloses document separating apparatus in which two high friction drums placed side by side are opposed by a counter-rotating resilient friction stripper belt supported between two pulleys one of which is driven. The belt is deflected and stretched taut over a free-wheeling pulley, coaxial with the drums, between the drums and of a slightly smaller diameter. The friction belt is driven in opposition to the friction drums which pull the document closest the drum along the document path. Such a structure works very well in connection with new money or with money in most conditions of use, as well as with stiffer documents of all sorts. However, some documents become so limp that they develop a cloth-like texture and tend to conform closely to the shape of the surfaces by which they are contacted in the device. Currency or other documents which are limp tend to have a special problem relative to a tendency to curl and develop small tears along their edges. Additionally, the taut friction stripping belt used in the past tends to cause edges of limp bills to curl and the bills to skew as it forces the bills into conformance with the idler pulley between the friction drums. Skewing, in turn, can cause bills to partially overlap and produce errors in counting as well as resulting in problems in stacking.
In an effort to accommodate to the different conditions of currency, an adjustment has been provided on machines in the past which allows the stripping friction belt to be held taut when processing new currency or other types of firm documents and to be slackened somewhat when worn currency is introduced. However, the touch required to handle these extremes has proven somewhat critical and the required adjustment has not been made successfully in some instances, without taking great pains causing problems for the users of the various machines.
In application Ser. No. 328,951, filed Dec. 9, 1981, there is disclosed a document separating apparatus of the above-described type capable of separating new currency without adjustment or at least with only minor adjustment which is much less critical than adjustments which have had to be made in the past. This apparatus employs a slack friction belt and interposes between the belt supporting pulleys a third idler pulley opposite the region where the belt wraps around the free-wheeling pulley between the friction drums. Opposition diameters of the third pulley are preferably just bearly out of contact with the belt when no documents are passing through. The third pulley is movably mounted so it can change position and has rim portions which contact respective friction drums. In use, because of the force of the friction belt on it, limp money conforms to an idler pulley between the friction drum members and displaces the third pulley only the thickness of the money. As stiff currency passes through, however, the belt itself is lifted out of the groove and away from the belt deflecting idler pulley. Lifting the friction belt causes the belt to engage the third pulley which also displaces the third pulley toward the part of the belt at its opposite diameter. Thus, this action causes the belt to tension at that opposite side as well as at the place it is displaced by the money, and thereby even further increasing the tension which improves the stripping effect on the stiffer bills as they pass through. At such times the rim portions of the pulley are capable of being lifted out of contact of the stiffer money. However, when the currency is limp, the rim portions of the third pulley that would ordinarily rest on the friction drum surfaces now rest on part of the limp paper money on the side thereof opposite the friction drum surfaces and effectively act as guides to stabilize and provide equal forces to each drive to further help in preventing skewing of the money as it passes through.
While the above-described devices are capable of processing a wide range of new and used paper currency, they can jam when they encounter a sheet having a severely curled leading edge. The badly curled edge tends to push the sheet backwardly toward the stack and the sheet never enters the nip between the drum and the belt where the feeding action occurs.
A common problem with all friction type feeding devices including those of the above-described type is that the stripping means usually has a friction coefficient of about one half that of the feed means. When a document enters the feeding area, i.e., the nip between a feed roller and a fixed or counter-rotating stripper, the higher friction feed roller conveys the bottom document through the apparatus while the succeeding document is held back. Because the friction means is a stripper device, under some conditions it is difficult to get the document into the feeding area far enough to be driven by the feed means. This is particularly difficult when documents have curled or torn edges, such as found on some circulated currency. In the prior art devices, as shown in FIG. 7 of the drawings, a spring loaded device is used to urge the documents with a light force into the nip of the feed stripper means. Typically such devices comprise a flat spring or a spring loaded ball bearing contacting the feed roller just prior to the stripping means. A critical adjustment of the spring device is usually required because an excessive force between the spring device and the feedroll will tend to lock the documents together (a condition referred to in the art as "fiber lock") making them difficult to separate. Moreover, these low friction devices usually will not straighten out curled leading edges whereby jamming, tearing and skewing of the documents can result.